1. Field of the Invention
This invention relates to machine tools and is particularly although not exclusively applicable to grinding machines including grinding machines for grinding the blade tips of multi-stage turbine or compressor rotors.
2. Description of the Prior Art
Machine tools are commonly known in which a workpiece rotates about a fixed axis and a rotary tool having a peripheral cutting face is traversed towards and away from the workpiece surface to carry out a cutting operation on the workpiece surface. In order to adjust the angle of cut with respect to the workpiece axis, the rotary cutting tool has a mounting which permits rotational adjustment of the tool to provide the required angle of cut. Such an arrangement requires considerable setting time in order to set the angle of cut correctly with the location of cut at the correct station on the workpiece since adjusting the angle of cut disturbs other adjustments of the tool.
In the case of blade tip grinding, the radius of the blade tips are given with reference to a longitudinal dimension from a datum. On a normal "Universal" grinding machine the pivot axis, about which the grinding wheelhead is pivoted for the various angles, is remote from the periphery of the grinding wheel. This necessitates angular adjustment to a much higher accuracy, than that required by the actual component, in order to establish the correction required in both the radial and longitudinal axes for the various angles. In practice this precludes an automatically sequenced machine, as there is no positive method of checking the position of the grinding wheel periphery.